A premix burner operating in a pressurized combustion chamber presents some unusual pilot and ignition problems. The use of an atmospheric naturally aspirated pilot burner is not satisfactory because the intermittently pressurized combustion chamber produces unstable pilot burner operation. The source of air for a pressure pilot is also limited. When the main gas is fed into the inlet of the combustion air blower there is no continuous source of air which can be used in an air gas mixer for the pilot burner. The present invention overcomes the problem by a take-of connection from the blower discharge plenum to the pilot burner air gas mixer chamber so that when the blower is operating initially only combustion air is supplied through the connection to the pilot mixture and when the main valve opens a mixture of air and gas is supplied under pressure to the pilot burner from the blower and in addition gas is supplied to the pilot burner from the pilot burner gas source.